Endangered: Numbers declining due to coastal development. (The Rockport Beach colony and some others in Texas are protected.)

Kathy and I went to Rockport Beach a few weeks ago to photograph a colony of black skimmers, crow-size birds at once elegant and peculiar looking.

What makes them elegant is a jet-black cap and back, offset by a rich white belly and neck markings, along with a red and black beak. But that beak, shaped like a butcher knife with the lower mandible jutting out, also makes them peculiar.

Another peculiarity is their elliptical, catlike pupils, unique for a bird. It apparently protects their retinas from the glare of sunlight on the beaches where they live.

Indeed, every aspect of this bird suits it to a beach environment. Its black upper side and white underside counterbalance light. Sunlight strikes the top, casting the belly in shadow - which then blends in with the bright sand.

So good is this camouflage that I nearly overlooked a group of the birds splayed out on the beach, wings held tightly against their bodies, beaks flat on the ground. This behavior, called loafing, helps the birds conserve energy during the heat of the day.

In early morning, late afternoon and even at night, skimmers go fishing. Their beaks are designed to scoop up fish; flying just inches above the water, the birds drop the knifelike lower mandible just beneath the surface. When it contacts fish, the bird lowers its head, sometimes into the water, and the upper mandible, or maxilla, snaps shut like a trap.

The birds glide over the water either on motionless wings held at a dihedral or on shallow, fluttery wing beats. When angling up in flight, they fly gracefully and fluidly on long, narrow wings.

Their nimble flight becomes quite aggressive when they're protecting their young. I experienced it firsthand, strolling too close to fluffy white chicks the size of Ruby Red grapefruits.